The present application relates to methods for reducing the contact resistance in semiconductor structures, and particularly to methods for reducing the resistance for a copper interconnect landing on middle-of-the-line (MOL) contacts having a multilayered structure (e.g., bilayer), and to semiconductor structures manufactured therefrom.
Semiconductor structures manufactured using conventional methods in the art may have difficulties with providing a low resistance via contact to a back-end-of-the-line (BEOL) interconnect structure. In addition, semiconductor structures manufactured by conventional processes may also have difficulties in providing an MOL contact which has lower lateral resistance across the MOL contact and an MOL contact which provides lower vertical resistance down to semiconductor devices located in and/or on the semiconductor substrate.
For instance, a conventional BEOL module has challenges in meeting demanding product electrical specifications which may require reduced overall resistance of the MOL contact to the first conductive via (V0) to the first metallization layer (M1). One of the major contributors to high resistance is the via contact resistance. Traditional V0M1 integration involving copper (Cu) vias and a tantalum nitride (TaN)/tantalum (Ta) liner landing on tungsten (W) contacts has difficulties overcoming the high resistivity of the thin TaN/Ta bilayer film at the bottom of the via of the BEOL interconnect.
Other liner options used in the conventional art, such as cobalt, rather than TaN/Ta, may actually increase the via contact resistance. Further, other conventional integration schemes place a liner at an interface between the Cu via and the MOL contact, which can lead to higher via contact resistance and reduced performance of the semiconductor structure.
In addition, some methods in the conventional art used for forming the MOL contacts employ tungsten. However, tungsten may have limitations on the lateral resistance of the MOL contact. Other methods used in the conventional art which attempt to reduce the MOL lateral resistance by forming MOL contacts having a metal bilayer structure still fail to adequately reduce the lateral resistance of the MOL contact because in these conventional fabrication methods, the MOL contact and the BEOL modules are manufactured separately, which in turn leads to a liner being formed at the entire interface between the MOL contact and the via contact of the BEOL interconnect and another liner being formed at the entire interface between the metal layers of the bilayer metal MOL contact. The liner formed at the entire interface between the metal layers of the bilayer metal MOL contact may lead to higher lateral resistance across the MOL contact, and the liner formed along the entire interface between the MOL contact and the via contact may in turn lead to higher via contact resistance and reduced performance for the semiconductor structure.